Suction pipe models are described, for example, in the patent specifications EP 0 820 559 B1 and EP 0 886 725 B1.
An internal combustion engine is basically designed in such a way that it has a fuel consumption which is as low as possible at a power which is as high as possible and/or a level of pollutant emissions which is as low as possible. For this purpose, it is necessary, for example, to know an air mass flowing into the combustion chamber of a cylinder of the internal combustion engine as accurately as possible. This can be determined by means of a suction pipe model, for example, as a function of a degree of opening of a throttle valve of the internal combustion engine. If the internal combustion engine has an external exhaust gas recirculation pipe by means of which exhaust gas from an exhaust tract of the internal combustion engine can be fed once more to a combustion process in the combustion chamber, then the fresh air mass flowing in via the throttle valve and the recirculated exhaust mass flow into the cylinder. The recirculated exhaust gas mass can, for example, be determined by means of an exhaust gas recirculation model. The exhaust gas recirculation model is similar to the suction pipe model, wherein only the parameters, for example a cross-sectional area of an exhaust gas recirculation valve, are modified, and/or wherein, for example, a degree of opening of the exhaust gas recirculation valve is a typical input variable of the exhaust gas recirculation model.